1. Technical Field
The present invention relates an optical position detecting device which optically detects the position of a target object, and a display device with a position detecting function having the same.
2. Related Art
As an optical position detecting device which optically detects the position of a target object, a technique has been proposed which detects a position when light emitted from a light projection means is blocked by an indicating device and detects the light emitted from the indicating device to thereby detect the position of the indicating device (refer to JP-A-2005-173684).
However, in the case of the technique of using the light emitted from the indicating device, since input through a finger, hand or the like is not possible, its usage is limited.
Accordingly, as schematically shown in FIG. 14, the inventor has studied an optical position detecting device in which a detection light source 12 is disposed to face an end portion of a light guiding plate 13, and a reflected light obtained as a detection light L2 exiting from the light guiding plate 13 and contacting a target object Ob of a finger is detected by a light detector 30. In such an optical position detecting device, the detection light L2 exiting from the light guiding plate 13 forms a light intensity distribution in which a light intensity monotonically decreases toward a side away from the side where the detection light source 12 is disposed, in an exiting space of the detection light L2. Accordingly, it is possible to detect the position of the target object Ob on the basis of the detection intensity in the light detector 30. According to such a technique, the target object Ob may be a finger or the like, and need not necessarily to be a light emitting indicating device.
However, in the method shown in FIG. 14, in a case where there exist portions having different reflection rates on the surface of the target object Ob, for example, in a case where there is a partial color difference or gloss difference on the target object Ob, even though the target object Ob is disposed in the same position, the detection intensity in the light detector 30 is changed, thereby deteriorating the detection accuracy.